Spray Characteristics of Simplex Swirl Atomizers

Abstract

The effects of air and liquid properties, and atomizer dimensions, on the spray characteristics of simplex pressure-swirl atomizers are examined. Mean drop size and drop-size distribution are measured using an improved form of light-scattering technique. The test range includes wide variations in air pressure, atomizer flow number, liquid flow rate, liquid viscosity and injection pressure differential. The effects on mean drop size and drop-size distribution of variation in distance between the atomizer and the plane of measurement are also examined. The results show that increase in distance from the nozzle, beyond the minimum needed to complete the atomization process, produces both an increase in mean drop size and a broader distribution of drop sizes in the spray. In fact, it is generally observed that any change in air properties, liquid properties and atomizer geometry that lowers the mean drop size, also narrows the drop-size distribution in the spray. It is also shown that conventional power law expressions for describing the dependence of mean drop size on air and liquid properties are basically unsound and have only limited ranges of application.